A shock-tube study of the N₂O + M ⇄ N₂ + O + M (M = Ar) rate constant using N₂O laser absorption near 4.6 µm

The low-pressure limit rate constant k_1,0 of the reaction N₂O + M ⇄ N₂ + O + M was measured in shock-heated mixtures of 0.2% N₂O/Ar using 4.56-µm laser absorption of N₂O in the temperature range 1546–2476 K near 1.3 atm. Modeling the N₂O profiles with a detailed kinetic analysis, which considered non-ideal pressure variations, provided k_1,0 values that were best fit by the expression k_1,0=1.01×10¹⁵exp(−30,050/T), with k_1,0 in cm³mol^–1s^–1 and T in K. Estimated k_1,0 uncertainties at 1546, 1821, and 2230 K were respectively 13.0%, 8.9%, and 9.0%. By combining the results of the present study with previous low-temperature data measured in flow/static reactors, the best fit over the temperature range 850–2500 K was determined to be (k_1,0 in cm³mol^–1s^–1, T in K) k_1,0=(1.04±0.04×10¹⁵)exp[(−30,098±90)/T]. This is the first study of k_1,0 using N₂O infrared laser absorption. Through the high signal-to-noise ratios of the experimental N₂O profiles and careful consideration of dP/dt effects, this k_1,0 determination is in excellent agreement with the large body of historical k_1,0 data but demonstrates significantly less scatter than all previous measurements.